JP2015122280A - Electro static charge removal mechanism and time-of-flight type mass spectrometer using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electro static charge removal mechanism capable of securely removing electro static charge of an insulation member in a vacuum environment in a simple configuration and to provide a time-of-flight type mass spectrometer including the same.SOLUTION: The electro static charge removal mechanism includes: a conductor member 6 slidably grounded by being in contact with a surface of an insulator member 3 disposed in a vacuum environment; a moving mechanism for sliding the conductor member 6 all over an exposed surface to a vacuum environment of the insulator member 3; and control means of the same.

Description

  The present invention relates to a mechanism for removing charge of an insulator member in a vacuum atmosphere, and a time-of-flight mass spectrometer using the mechanism.

  In a time-of-flight mass spectrometer (TOFMS), generally, ions from an ion source are accelerated by an electric field to give the ions kinetic energy proportional to their charge, and the accelerated ions The mass-to-charge ratio of the ions is obtained by measuring the time that the aircraft flies a certain distance.

  Various types of ion sources have been put into practical use. For example, ion sources based on Matrix Assisted Laser Desorption / Ionization (MALDI) are used for protein analysis. In addition, a combination of this and a quadrupole ion trap is widely used (see, for example, Patent Document 1).

  In such MALDI-TOFMS, normally, an Einzel lens is arranged between an extraction electrode and an ion trap arranged opposite to a laser irradiation position of a sample to converge ions, and then the ion trap. Leads to the ion entrance.

  Insulation is important because a high voltage is applied to the Einzel lens, and the three electrodes forming the Einzel lens are each supported by a support made of an insulator. However, in MALDI-TOFMS measurement, ions are caused to fly using an electric field in a vacuum atmosphere, and therefore, when used for a long time, positive or negative valence electrons are trapped on the insulator surface (hereinafter referred to as “charging”). ") Occurs. There is a high possibility that current leakage is induced by charging of the surface of the insulator, and when current leakage occurs, there is a risk of serious damage to electronic components such as detectors.

  In addition, various inconveniences such as a measurement error due to a change in the electric field that limits the ion trajectory due to charging of the insulator surface occur.

  As a method for removing valence electrons from the surface of an insulator in a vacuum atmosphere, conventionally, a method has been proposed in which ionized nitrogen gas or oxygen gas is used as a neutralizing gas and the neutralizing gas is sprayed (for example, a patent). Reference 2).

  As another method for removing valence electrons from the charged insulator surface, a method of diffusing the valence electrons by spraying a high temperature gas has been proposed (for example, see Patent Document 3). In this method, the sample in the main sample chamber is hermetically covered with a sub-sample chamber having a narrow space in order to prevent gas diffusion into the vacuum main sample chamber while removing the valence electrons on the sample surface. The inside of the sub sample chamber is evacuated while high temperature gas is blown into the sub sample chamber in a state in which the inside is cut off from the vacuum atmosphere of the main sample chamber.

JP 2013-104741 A Japanese Patent Laid-Open No. 10-189544 Japanese Utility Model Publication No.5-1155

  By the way, in order to carry out the charging removal method disclosed in Patent Document 2, the troublesome work of grasping the charging state and adjusting the neutralization adjustment by blowing the necessary amount of neutralizing gas is required. Become. In addition, since the degree of vacuum in the vacuum atmosphere deteriorates during static elimination, when this technique is applied to TOFMS, there is a problem that TOFMS measurement cannot be performed until the degree of vacuum is recovered after static elimination work.

  On the other hand, in the method disclosed in Patent Document 3, consideration is given to the deterioration of the degree of vacuum. However, in order to apply this method to TOFMS, each insulator supporting the electrode is enclosed in an airtight manner. In addition, a complicated mechanism of exhausting while blowing high-temperature gas into the interior surrounding each insulator is required, and cannot be practically adopted.

  In the present invention, for example, charging of the surface of an insulating member such as an electrode supporting member in a vacuum chamber of TOFMS can be reliably removed with a simple configuration without deteriorating the degree of vacuum. It is an object of the present invention to provide a TOFMS that can eliminate the risk of current leakage and perform stable mass measurement by applying the mechanism and the charge removal mechanism to the electrode support member.

  In order to solve the above problems, the charge removal mechanism of the present invention is a mechanism for removing the charge of an insulator member disposed in a vacuum atmosphere, and is slidable in contact with the surface of the insulator member. It is characterized by comprising a grounded conductor member, a moving mechanism for sliding the conductor member over the entire exposed surface of the insulator member in a vacuum atmosphere, and a control means thereof. 1).

  Here, in the charge removal mechanism of the present invention, the actuator of the moving mechanism is made of a shape memory alloy, and the control means includes a power source for energizing and heating the shape memory alloy and a control means thereof (Claim 2). Can be suitably employed.

  The charge removal mechanism of the present invention will be described more specifically. The insulator member is a columnar member, and its peripheral surface is exposed in a vacuum atmosphere. The conductor member is contact-fitted to the columnar member. The actuator is made of a shape memory alloy spirally wound along the outer periphery of the insulator member, and the conductor member is fixed to one end side of the ring member. Item 3).

  On the other hand, the time-of-flight mass spectrometer of the present invention is provided with an electrode in the vacuum chamber for extracting ions from the ion source by an electric field and guiding them in a predetermined direction. In a time-of-flight mass spectrometer that includes an ion detector that detects ions accelerated by an electric field of electric field strength after passing through a specified flight region, and obtains the mass-to-charge ratio of ions from the time to reach the detector, A support member made of an insulator that supports the electrode is characterized by being provided with the charge removing mechanism according to any one of the first, second, and third aspects (claim 4).

  The present invention eliminates the charge generated on the surface of the insulator member in the vacuum atmosphere by directly contacting the grounded conductor member, that is, by removing the charge by a purely mechanical process. It tries to solve the problem.

  That is, the charge on the surface of the insulator member can be removed by bringing a conductor member such as a grounded metal into contact, and the conductor member is spread over the entire area of the insulator member exposed in the vacuum atmosphere. By making sliding contact, the charge on the entire surface of the insulator member can be removed, and there is no need to use gas as in the conventional charge removal method, so the vacuum degree of the vacuum atmosphere is not deteriorated at all. Can be done.

  Using a shape memory alloy as the actuator of the conductor member movement mechanism, heating it with electric resistance, and returning it to the memorized shape when it reaches the transformation point, it is extremely simple mechanically Moreover, the control becomes easy.

  Further, as a more specific configuration, the insulator member has a columnar shape, and the conductor member is a ring-shaped member that contacts and fits to the outer peripheral surface of the insulator member, and the actuator uses a shape memory alloy of the insulator member. By adopting a structure in which a ring-shaped conductor member is fixed to one end of the coil spring that is spirally wound along the outer peripheral surface, a simple mechanism can be obtained while obtaining a large stroke. A compact charge removal mechanism can be realized.

  By applying the electrostatic elimination mechanism as described above to the electric field forming region of the TOFMS, that is, an insulator support member between the three electrodes of the Einzel lens, for example, the vacuum degree of the vacuum chamber can be reliably reduced. In addition, the charge of the insulator member can be removed.

  According to the present invention, charging on the surface of the insulator member in a vacuum atmosphere can be reliably removed without any deterioration in the degree of vacuum. Further, by using, for example, a coil spring-shaped shape memory alloy as the actuator of the conductor member that is in sliding contact with the insulator member, the above-described effects can be realized with a compact and simple configuration. In addition, shape memory alloys are suitable for actuators in a vacuum atmosphere where it is desired to reduce the amount of emitted gas because they are metals that can obtain a corresponding stroke in a small volume.

  The above charge removal mechanism is applied to the insulator of the electrode support member in the electric field forming region in the vacuum chamber of the TOFMS, and the charge removal mechanism is operated at any given time of operation or as necessary. Thus, it is possible to eliminate the risk of current leakage and perform stable mass measurement.

Sectional drawing showing the non-operation state (a) of the charge removal mechanism and the operation state (b) of the charge removal mechanism in the embodiment of the present invention. The external perspective view corresponding to FIG. 1 which abbreviate | omitted and showed the upper electrode. The schematic sectional drawing which shows the structural example of MALDI-TOFMS using the charge removal mechanism of this invention. The top view (a) and BB sectional drawing (b) of the Einzel lens of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1A and 1B are longitudinal sectional views of an embodiment of the present invention, in which FIG. 1A shows a non-operating state of a charge removal mechanism, and FIG. 1B shows an operating state thereof. 2 is an external perspective view showing the upper electrode 2 of the embodiment of FIG. 1 with the illustration omitted, and (a) and (b) correspond to (a) and (b) of FIG. 1, respectively. Thus, the non-operating state and the operating state of the charge removing mechanism are shown.

  An upper electrode 2 is supported on the lower electrode 1 via a cylindrical insulator spacer 3, and these are all disposed in a vacuum atmosphere. The surface of the insulator spacer 3 may be charged by an electric field generated by the electrodes 1 and 2 or neighboring electrodes (not shown).

  In the lower electrode 1, a recess 1a having a diameter larger than the diameter of the insulator spacer 3 by a predetermined dimension is formed at the position where the insulator spacer 3 is disposed, and in the recess 1a, a coil shape is formed. The formed shape memory alloy actuator 4 and the lower end of a return spring 5 made of a tension coil spring are accommodated, and this recess 1a forms these spring seats. The shape memory alloy actuator 4 and the return spring 5 are wound in a coaxial spiral along the outer periphery of the insulator spacer 3.

  A conductor ring 6 made of metal or the like is fixed to the upper end of the shape memory alloy actuator 4. The conductor ring 6 is slidably fitted with its inner peripheral surface in contact with the outer peripheral surface of the insulator spacer 3. Further, the upper end portion of the return spring 5 is also fixed to the conductor ring 6. The return spring 5 is made of metal, and the lower end thereof is mechanically and electrically connected to the lower electrode 1 and the upper end thereof is connected to the conductor ring 6.

  The shape memory alloy actuator 4 can be supplied with power from the power source 7 through the wiring 7a. The power source 7 is placed under the control of the control unit 8 and satisfies several other conditions, for example, that the electrodes 1 and 2 are both at the ground potential when operated by an operator, for example. In this case, the shape memory alloy actuator 4 is supplied with power. By this power supply, the shape memory alloy actuator 4 is heated by its own electrical resistance, and when the temperature reaches the transformation point, the shape memory alloy actuator 4 returns to the memorized shape. In the present embodiment, the shape when the transformation point is reached, that is, the memorized shape is the shape shown in FIGS.

  That is, the shape memory alloy actuator 4 is freely deformed during normal use of the apparatus including the electrodes 1 and 2, that is, in a state where no power is supplied to the shape memory alloy actuator 4. In this state, the shape memory alloy actuator 4 is restored by a tension coil spring. Due to the elastic force of the spring 5, the spring 5 is housed in the recess 1 a as shown in FIGS. Therefore, in this state, the conductor ring 6 is positioned in contact with the upper surface of the lower electrode 1.

  When power is supplied to the shape memory alloy actuator 4 and the temperature reaches the transformation point, the shape memory alloy actuator 4 returns to the shape shown in FIGS. At the time of return, the conductor ring 6 fixed to the tip is in sliding contact from the lower end portion to the upper end portion along the outer peripheral surface of the insulator spacer 3. Since the conductor ring 6 is connected to the lower electrode 1 having the ground potential via the return spring 5, almost the entire area exposed in the vacuum atmosphere of the insulator spacer 3 contacts the conductor ring 6 having the ground potential. As a result, the charge on the surface is reliably removed.

  Here, in the above embodiment, the insulator spacer 3 has a cylindrical shape, but its cross-sectional shape is not particularly limited. If the cross-sectional shape is uniform in the axial direction, any shape such as a polygon can be used. can do. Of course, the conductor ring 6 needs to have an inner peripheral surface having the same shape as the cross-sectional shape of the insulator spacer 3.

  Further, in order to ensure that the inner peripheral surface of the conductor ring 6 comes into contact with the outer peripheral surface of the insulator spacer 3, a gasket-like member made of a conductor may be attached to the inner peripheral side of the conductor ring 6. For example, a brush-like member in which a number of U-shaped spring-like protrusions are provided on the inner peripheral surface can also be employed.

  A specific application example of the above-described embodiment of the present invention is TOFMS. That is, since TOFMS extracts and converges ions by an electric field generated by applying a high-voltage current to an electrode provided in a vacuum chamber, an insulator member is used for insulating support of the electrode. The above-described embodiment is extremely useful as a mechanism for removing the charge of the insulator member.

  As an example, an example in which the present invention is applied to the MALDI-TOFMS shown in FIG. 3 is shown below. FIG. 3 is a cross-sectional view showing a schematic configuration of a MALDI-TOFMS provided with an ion trap.

  Since the basic configuration of the MALDI-TOFMS provided with this ion trap is well known, a detailed description thereof will be omitted, but the overall configuration will be briefly described. The sample S on the sample stage 11 is irradiated with the laser light L. The ions generated thereby are extracted by the extraction electrode 12, converged by the Einzel lens 13, and then guided into the quadrupole ion trap 14. The ions introduced into the quadrupole ion trap 14 are once trapped there, and ions having a specific mass-to-charge ratio are selectively discharged as precursor ions in the quadrupole ion trap 14 and others are discharged to the outside. After that, the CID gas is introduced into the quadrupole ion trap 14 to excite the precursor ions, dissociate by colliding with the CID gas, and discharged to the flight region 15. Ions flying in the flight region 15 are detected by the detector 16, and the mass-to-charge ratio of the ions is obtained from the time required for arrival. All the above components are accommodated in the vacuum chamber 17.

  The Einzel lens 13 has a structure in which three ring-shaped electrodes 13a, 13b, and 13c are arranged coaxially as shown in a plan view in FIG. 4A and a cross-sectional view along BB in FIG. And three insulator spacers 20 are interposed between the ring-shaped electrodes 13a and 13b and 13b and 13c, respectively. Similarly, the lowermost ring electrode 13a is supported on the extraction electrode 12 via three insulator spacers 20 in the same manner. Each of these insulating spacers 20 is provided with the charge removing mechanism shown in FIGS.

  That is, a conductor ring 21 is fitted in each insulator spacer 20, and the conductor ring 21 is slidable in contact with each insulator spacer 20. Although not shown in FIG. 4, the recesses 1a shown in FIGS. 1 and 2 are formed in the respective electrodes below the positions where the insulator spacers 20 are disposed. The illustrated shape memory alloy actuator 4 and the return spring 5 are accommodated, and each shape memory metal actuator 4 is connected to a power source 7 and its control unit 8, which is the same as the embodiment shown in FIGS. In addition, by supplying power to each shape memory alloy actuator 4 according to a command from the operator, each conductor ring 21 slides upward along the outer peripheral surface of each insulator spacer 20, and the outer peripheral surface is charged. Remove.

  By providing such a charge removal mechanism, it is possible to reliably remove the charge on the surface of each insulator spacer 20 by giving an electrostatic removal command after using MALDI-TOFMS for a certain period of time or longer. Can do. As a result, there is no risk of current leakage, and mass spectrometry measurement is stable.

1, 2 Electrodes 3 Insulator spacer (insulator member)
4 Shape memory metal actuator 5 Return spring 6 Conductor ring (conductor member)
7 Power supply 8 Control unit 11 Sample stage 12 Extraction electrode 13 Einzel lens 14 Quadrupole ion trap 16 Detector 17 Vacuum chamber L Laser light

Claims (4)

A mechanism for removing the charge of an insulator member arranged in a vacuum atmosphere,
A conductor member that is slidably grounded in contact with the surface of the insulator member, a moving mechanism for sliding the conductor member over the entire exposed surface of the insulator member in a vacuum atmosphere, and A charge removal mechanism comprising a control means. 2. The charge removing mechanism according to claim 1, wherein the actuator of the moving mechanism is made of a shape memory alloy, and the control means is a power source for energizing and heating the shape memory alloy and the control means. The insulator member is a columnar member, and its peripheral surface is exposed in a vacuum atmosphere, and the conductor member is a ring-shaped member that contacts and fits to the columnar member, and the actuator includes the insulator member The charge removing mechanism according to claim 2, wherein the conductive member is fixed to one end of the shape memory alloy wound around the outer periphery of the shape memory alloy. In the vacuum chamber, an electrode for extracting ions from the ion source by an electric field and guiding them in a predetermined direction is provided, and ions provided in the vacuum chamber are accelerated by an electric field having a known electric field strength. In a time-of-flight mass spectrometer that includes an ion detector that detects after passing through the flight region and calculates the mass-to-charge ratio of ions from the time to reach the detector,
A time-of-flight mass spectrometer, wherein the support member made of an insulator that supports the electrode is provided with the charge removal mechanism according to any one of claims 1, 2, and 3.

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